fs/buffer: use sleeping lookup in __getblk_slowpath()

Just as with the fast path, call the lookup variant depending
on the gfp flags.

Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Link: https://lore.kernel.org/20250515173925.147823-2-dave@stgolabs.net
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: Davidlohr Bueso

fs/buffer.c

@@ -1122,6 +1122,8 @@ static struct buffer_head *
 __getblk_slow(struct block_device *bdev, sector_t block,
 	     unsigned size, gfp_t gfp)
 {
+	bool blocking = gfpflags_allow_blocking(gfp);
+
 	/* Size must be multiple of hard sectorsize */
 	if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
 			(size < 512 || size > PAGE_SIZE))) {
@@ -1137,7 +1139,10 @@ __getblk_slow(struct block_device *bdev, sector_t block,
 	for (;;) {
 		struct buffer_head *bh;
 
-		bh = __find_get_block(bdev, block, size);
+		if (blocking)
+			bh = __find_get_block_nonatomic(bdev, block, size);
+		else
+			bh = __find_get_block(bdev, block, size);
 		if (bh)
 			return bh;